[nudephil (OP)]

An interesting conundrum from listener James:

I bought a car. I'm naïve regarding vehicles and I didn't look under the bonnet. It now is throwing up wiring issues after only 3 weeks. A rat has clearly eaten at a few parts, particularly the foam that's there for sound proofing.

I am convinced it was chewed prior to me buying the car. Is there any way to "carbon date" the rat bites on the foam?

[Bored chemist]

Take a picture.
Wait a week.
Take another picture.
If the pictures are essentially the same there's nothing eating your car now, so it must have happened earlier.

Or you can look for rat droppings with plastic foam in at the previous owner's garage.

[Hayseed]

Did it run alright a day or two after you bought it?  Have you rodents in your area?  Any debris on floor under car at your place?